Genetic Therapy of Surfactant Protein Deficiency Pulmonary surfactant is a complex mixture of phospholipids and protein, which spreads as a monomolecular film along the surface of the alveolar epithelium. Surfactant insufficiency or dysfunction leads to alveolar collapse which greatly increases the effort required to aerate the lung, a condition referred to as respiratory distress syndrome (RDS). SP-B, a 79 amino acid, hydrophobic surfactant-associated peptide, promotes the rapid formation of a surface film following surfactant secretion. Mutations resulting in the lack of SP-B expression in newborn human infants invariably lead to neonatal rds with fatal outcome. The overall goal of this proposal is to design and test a treatment strategy involving adenoviral-mediated gene transfer in an animal model of SP-B deficiency. The specific aims of this proposal include: (1) The generation of a mouse model of SP-B deficiency, using the strategy of SP- B gene ablation by homologous recombination in murine embryonic stem cells; (2) characterization of optimal conditions for adenoviral-mediated expression of SP-B in neonatal wild type mice, including the dose of adenovirus required to achieve rapid and extensive expression, the cell- specificity of expression